The present invention relates to a device for delivering fluids, in particular, fuel.
One such device is described in DE 196 38 332 A1. This device has a drive shaft, which, for example, is indirectly rotatably driven by means of an internal combustion engine. In addition, the device has a supply or delivery pump, which has at least one supply member that is coupled to a drive shaft. The drive shaft drives the drive shaft by means of a gear, which, by way of example, is a spur gearing having a constant gear ratio. This known device serves to deliver fuel to a high-pressure pump, which, in turn, supplies fuel under high pressure to injection sites on the internal combustion engine. Driving of the delivery pump takes place with a rotational speed which is proportional to the rotational speed of the internal combustion engine. Upon starting the internal combustion engine, when this is only driven with a low rotational speed, the supply pump is correspondingly driven with a low rotational speed, so that, under these circumstances, a fuel volume is supplied which is too small to ensure starting of the engine.
Particularly, with a higher fuel temperature and a lower rotational speed of the internal combustion engine, for example, due to insufficient voltage of a vehicle voltage source used to start the engine, insufficient fuel quantities are supplied by the delivery pump. The gear ratio of the gear could therefore be modified so that the supply pump is driven with a higher rotational speed or the supply pump could be so dimensioned that it supplies a larger fuel volume. However, then, upon normal operating rotational speed of the internal combustion engine by the supply pump, an excessively large fuel volume would be delivered, which must be controlled.
In contrast to the above-described device, the device of the present invention provides the advantage that, through the use of a tapered ring gear, the supply pump is driven with a variable gear ratio, which, with smaller rotational speed of the drive shaft and a lower supply pressure, is larger, so that the supply pump is driven with a higher rotational speed. With a higher rotational speed of the drive shaft and a higher supply pressure, the supply pump is driven with a variable gear ratio that is smaller so that the supply pump is driven with a correspondingly lower rotational speed. Therefore, an increase of the supply volume with a lower rotational speed of the drive shaft is obtained, without proportionally increasing the supply volume upon a higher rotational speed of the drive shaft. The present invention also contemplates a simple manner for producing the tapered ring gearing depending on the supply pressure.